Fish gelatin as an alternative to mammalian gelatin for food industry: A meta-analysis

Highlights

• A meta-analysis of fish gelatin comparing to mammalian gelatin was conducted.

• The overall gel strength of fish gelatin is lower than mammalian gelatin.

• The gel strength of warm-water fish gelatin is higher than cold-water fish gelatin.

• The warm-water fish gelatin is more suitable for food gelling applications.

Abstract

Gelatin is prepared from heat denaturation and partial hydrolysis of collagen from mammalian sources and is a common ingredient in the food industry. Diet restrictions of porcine gelatin due to culture and/or religion, and the health safety concerns due to an onset of zoonotic disease in cattle from earlier period, have led to the search for alternative gelatin sources. The most extensively studied alternatives with high potential are fish and fish by-products. However, fish gelatin application in the food industry is still limited due to inferior performance in gelling ability. The gel strength values of the warm-water and cold-water fish gelatin compared to mammalian gelatin, were evaluated by meta-analysis to determine their potential as an alternative. Through rigorous screening of the extraction and gel strength determination methods, a total of 13 studies were included in the analysis. The mean gel strength of fish gelatin was significantly lower in comparison to mammalian gelatin (p < 0.05). Interestingly, the warm-water fish skin gelatin was the only sample group with a combined effect estimate point that overlapped and extended pass the null effect line, making it the most suitable substitute of mammalian gelatin in food gel preparation when compared to other fish gelatins.

Introduction

Gelatin is a hydrocolloid food ingredient commonly used in the food industry due to its functional properties (Schrieber & Gareis, 2007). Gelatin can improve the viscosity, texture and stability of liquid and semi-solid food systems (Stevens, 2009). Gelatin is a thermoreversible protein gel-forming agent that can provide a unique melt-in-the-mouth effect upon consumption from having a melting point of 35–37 °C, which is close to human body temperature (Mariod & Adam, 2013).

Gelatin is commonly prepared by heat denaturation and partial hydrolysis of collagen, a fibrous protein component of the skin, bones, and cartilages of animals (Johnston-Banks, 1990). The raw materials used for commercial gelatin extraction are mainly from mammalian sources, with porcine skins and bovine hides making up to 42% and 29%, respectively, of the total gelatin market worldwide (Business Wire, 2017). However, there are limitations to using porcine gelatin in food formulated to serve consumers with cultural and religious dietary requirements, such as in Kosher and Halal foods. Furthermore, the onset of the bovine spongiform encephalopathy (BSE) in cattle had raised health safety concerns amongst the public towards bovine gelatin about the possibility of disease transfer to humans via consumption of contaminated foods. Although it was later shown that the production process was enough to ensure product safety, the gelatin industry was still negatively impacted by this health concern (Schrieber & Gareis, 2007; Sultana, Ali, & Ahamad, 2018). These reasons have led to numerous studies in search of alternative sources of gelatin. As a result, fish and fish by-products were widely studied as potential source of gelatin. Fish gelatin not only serves as a promising alternative to mammalian gelatin, it can also create economic value to the fish by-products and reduces the waste generated from the seafood industry (Muyonga, Cole, & Duodu, 2004). The fish processing industry generates large amounts of by-products from fish bones and skins during the production of fish fillets as product yields were only 30–50% (Stevens, Newton, Tlusty, & Little, 2018). Gelatin can be extracted from these by-products.

To date, the use of fish gelatin in the food industry is still limited as compared to gelatin of bovine and porcine origins (Business Wire, 2017; Sultana et al., 2018). The reason for the under usage of fish gelatin can be due to the presence of fishy off-notes (Wasswa, Tang, & Gu, 2007). Some studies have addressed this issue through an additional filtration processing step (Muyonga et al., 2004) or by using salts, base or acid pre-treatments, such as pre-treatment with 15 g/L NaCl, 2 g/L NaOH, 2 g/L sulfuric acid or 1 g/L citric acid (Tohmadlae, Worawattanamateekul, & Hinsui, 2019). Another important reason is the perceived inferior performance in the gelling ability of fish gelatin as compared to that of mammalian gelatin (Haug & Draget, 2009). This may be due to intrinsic factors like the chemical composition of the fish raw material which can vary between species and parts, and environmental factors like the temperature conditions of the fish natural habitat (Duan, Zhang, Xing, Konno, & Xu, 2011; Johnston-Banks, 1990; Koli et al., 2012; Muyonga et al., 2004). Although gelatin can be versatile, its primary use in the food industry is as a gelling agent. Therefore, gelling properties such as the gelling and melting temperatures and the gel strength are key functional considerations when assessing gelatin quality (Karayannakidis & Zotos, 2016). The gel strength is an important parameter for gelatin and commercially referred to as the “Bloom” value (Johnson-Banks, 1990). The gel strength and melting point can be influenced by the molecular weight, amino acid composition, and the ratio of the α- and β-chains of the gelatin molecule where the gelatin with a higher ratio of α-chains will have higher gel strength (Cho et al., 2004; Schrieber & Gareis, 2007).

Past studies have mainly focused on the optimization of the gelatin extraction process from particular fish species (Mahmoodani, Sanaei, See, Yusop, & Babji, 2014; Mohtar, Perera, & Quek, 2010; Sanaei, Mahmoodani, See, Yusop, & Babji, 2013). While gel strength values were reported, reports comparing gel strength between different fish species were scarce. To analyze the data from previous studies and to show the potential of fish gelatin as an alternative to mammalian gelatin in food applications, a meta-analysis was performed in this study. Meta-analysis is a formal quantitative study design that involves pooling the data of individual studies to improve the precision of the estimation of an effect of a treatment or other outcomes in contrast to considering each of study separately (Haidich, 2010). Thus, the present study focused on the gel strength as the effect or outcome of interest for comparing the treatments of cold-water fish and warm-water fish gelatin against their mammalian gelatin control from various studies.